Portable id-transmitter for an authentication system and an authentication operating system for use therewith

ABSTRACT

A portable ID transmitter for an authentication system of a vehicle includes a supply battery, a micro controller, UWB transmitting and receiving circuits controlled by the microcontroller for communication with a vehicle-side control device, and an LF receiving circuit controlled with the microcontroller for receiving LF wake-up signals transmitted in the LF frequency range, all arranged in a housing.

BACKGROUND

The invention relates to a portable ID transmitter for an authenticationsystem and a method for operating the authentication system. Inparticular, the invention refers to an authentication system with whicha portable ID transmitter can be authenticated to the vehicle to enablevehicle functions for an operator carrying the portable ID transmitter.

In prior art, different so-called keyless access systems are disclosed.They are based on radio communication between a vehicle infrastructureand a portable ID transmitter. In the context of the radio communicationcarried out, the desired authentication is performed, for example, byexchanging and checking encrypted authorization data.

The use of low-frequency (LF) and high-frequency (HF) radio waves isknown and widely used in keyless access systems. In prior art, combinedcommunication using LF/HF systems has also been disclosed.

With radio-based authorization systems, security, especially againstcompromising the radio communication carried out, is of decisiveimportance. When releasing a vehicle function using portable IDtransmitters, the determination of a position, a distance, or a similarquantity, for example, to check the plausibility of bidirectionalcommunication, is known from prior art. For example, it is known toevaluate the signal strength of an LF radio communication between aportable ID transmitter and a vehicle authentication system. Asupplementary or alternative concept to increase security againstcompromise can simply be based on limiting the transmission power of anLF communication. By limiting the transmission power of an LFcommunication between vehicle and ID transmitter, it is ensured that,for example, an LF alert signal transmitted from the vehicle to the IDtransmitter can only be received by the other communication partner if amaximum distance between ID transmitter and vehicle is not exceeded.

Many of the well-known authentication systems still have the fundamentaldisadvantage that an LF radio communication or an HF radio communicationcan be extended, for example, in the context of so-called relay stationattacks. To avoid such or other compromises, countermeasures arenecessary some of which, however, are quite costly.

Therefore, it is the objective of the invention to improve thewell-known authentication methods so that they provide an effective, butat the same time comparatively inexpensive protection against acompromise of the transmitted signals.

BRIEF SUMMARY

According to the invention, the objective is achieved with a portable IDtransmitter having the characteristics of claim 1 and with a methodhaving the characteristics of claim 12.

According to the invention, a portable ID transmitter for a vehicleauthentication system is provided. The ID transmitter comprises in ahousing:

-   -   a supply battery,    -   a microcontroller,    -   UWB transmission and reception circuits controlled by the        microcontroller for communication with a vehicle control unit,    -   an LF reception circuit coupled with the microcontroller for        receiving LF alert signals transmitted in the LF frequency        range.

The microcontroller is arranged to transmit, when the LF receptioncircuit has received an LF alert signal, a UWB signal for receptionthrough a UWB interface of the vehicle, which is coupled with thevehicle control unit. Furthermore, the microcontroller is arranged todetect the reception of a UWB response signal by the UWB transmissionand reception circuits, which also have a suitable UWB antenna. Inresponse to the recorded UWB response signal, the microcontroller candetect and evaluate the time difference between transmitting the UWBsignal and receiving the UWB response signal. The result of theestimation can be evaluated by the microcontroller to determine whetherthe time difference or a value derived from the time difference does notexceed a predetermined maximum value. According to the invention, themicrocontroller is configured to transmit a radio signal to the vehiclecontrol unit, which has a release value, depending on the result of thetest.

An essential aspect of the inventive method is based on the use ofultra-wideband communication.

In principle, the use of ultra-wideband radio signals (UWB radiosignals) is known for some prior art applications. However, market-readytransceivers have only recently become available for use.

The fundamentals of ultra-wideband technology have been known for a longtime. However, only recently this technology has become accessible foruse in a wide range of applications, not least through more liberalregulation.

Ultra-wideband technology involves a short-range radio communicationbased on the transmission of short signal pulses, which covers aplurality of frequencies within a large frequency bandwidth. Inparticular, the width of the frequency ranges covered depends on theregulatory requirements of the corresponding territorial area. Forexample, signals are modulated with On/Off keying, pulse amplitudemodulation, or pulse position modulation.

A disadvantage of UWB communication in relation to established LF and/orHF communication is the comparatively high energy requirement of manytransceivers currently available and suitable for UWB communication.

However, UWB communication has the basic advantage that, due to thetransmission of pulses, a distance is determined using a runtime-basedapproach, which is often referred to as the time-of-flight method. Forexample, the distance between the first UWB antenna and the portable IDtransmitter can be determined by transmitting a UWB signal from thefirst UWB antenna to the portable ID transmitter, which is responding toby a UWB transceiver of the portable ID transmitter, and the recordedresponse signal is evaluated by a unit coupled with the first UWBantenna, for example, a control means. This takes place by evaluatingthe time elapsed between transmission and reception. The distance to theID transmitter, the processing time within the ID transmitter, and thedistance from the ID transmitter to the first UWB antenna are taken intoaccount. If, as in this example, the running time is evaluated on thevehicle, only the processing time must be stored on the vehicle withinthe ID transmitter, so that a corresponding correction of the timemeasured on the vehicle can be made between transmission of the UWBsignal and reception of the UWB response.

Experience has shown that the accuracy of such a UWB-based distancedetermination is significantly higher at the magnitude of distancesusually provided than is the case of other methods, such as signalstrength determination, usually using RSSI measurement of HF or BLEcommunication. With the UWB-based distance determinations, accuracyfrequently ranges between 10 and 20 cm.

Because the pure running time of the UWB signal is relatively shortcompared to the processing time, due to the unexpectedly long total timebetween transmission of a UWB signal and reception of the correspondingresponse, it would be possible to detect an additional processing of thesignal, for example, for manipulating the signal in the context of arelay station attack. Therefore, compromises, for example, in the typeof the relay station attacks described, are only possible with verycomplex methods, if at all.

Another advantage resulting from the use of UWB signals is that due tothe plurality of frequencies used, shading of the signals is veryunlikely. This is because for at least some of the frequencies usedsimultaneously there is probably always a line of sight between thetransmitter and receiver. One reason for this is that for somefrequencies diffraction effects or reflections can be expected.

According to the invention, it is provided that the ID transmitter isequipped with hardware (sufficient computing power, storage means withsufficient storage capacity) and programmed in such a way that it candetermine completely independently the distance of the ID transmitterfrom a vehicle that has a UWB interface. The performance of thisdetermination comprises the transmission of a UWB signal by means ofwhich a vehicle UWB transceiver and/or a vehicle UWB antenna (which iscoupled to a control unit) correspondingly adapted to the ID transmitteris caused to emit a UWB response signal.

Furthermore, the determination comprises the correction of the timeelapsed between transmission of the UWB signal and reception of the UWBresponse signal by the time period for reception, evaluation, andtransmission processes required by the vehicle infrastructure aspreviously specified to the ID transmitter.

Basically, the essential aspect involves checking whether the timedifference detected is smaller than the specified maximum timedifference. The latter is predetermined in knowledge of theelectronically conditioned latency and as a specification of the maximumgranted running time of the radio radiation, which is directly linked toa maximum tolerated distance. For example, the electronically inducedlatency results from signal processing in the vehicle's control system.

The process of causing and recording the distance has the advantage thatthe ID transmitter is already aware—in contrast to the vehicle—that itis in the vicinity of the vehicle because the LF signal has alreadyalerted the ID transmitter. The distance measurement can thus beginwithout requiring a triggering process on the part of the motor vehicle.This can potentially reduce the time required to determine the distance.A further advantage involves that the LF signals, whose receptionrequires only very low energy consumption, have already produced aninitial pre-selection of ID transmitters to be potentially addressed.The number of UWB communications to be carried out on the vehicle canthus be significantly reduced, which results in energy savings.

Preferably, the radio signal involves a UWB signal.

If the check by the ID transmitter shows that the time difference doesnot exceed the predetermined value, the vehicle control unit isinformed. For this purpose, a release value is transmitted by means of aradio signal, in the simplest case, for example, a binary value or acode, which informs the vehicle control unit that the distance test bythe ID transmitter has led to the desired result.

According to one embodiment, the microcontroller is configured totransmit an authorization code by means of the radio signal.

For example, it can be provided that a challenge-response list may bestored on a storage medium of the ID transmitter, which storage mediumis coupled with the microcontroller. At the same time, it can beprovided that the microcontroller is configured to transmit by means ofthe radio signal a response value assigned to the challenge value if theUWB response signal comprises a challenge value.

According to a preferred further development, the ID transmitter isconfigured to test a plurality of LF signals for identityidentification, acquire signal strength values for the LF signals, andrespond to the reception of the LF signals with a HF response signal.Preferably, the HF response signal comprises the identity identifiers ofthe LF signal with the strongest signal strength value and/or a list ofidentity identifiers with the associated signal strength values.

This information can be used when implementing a suitable method, forexample, by a vehicle control unit, to prioritize the UWB antennas froma plurality of UWB antennas spaced apart on the vehicle, as to which ofthe UWB antennas is preferably controlled.

A predetermined minimum time interval after the HF response signal canbe provided for the UWB response signal. As a result, it is possible toanticipate an expected further movement of an operator towards thevehicle. This increases the probability that the operator issufficiently close to the vehicle that it is reached by the UWB signal.This eliminates the need to transmit an additional UWB signal if theminimum time interval (by empiricism and depending on the false triggersaccepted) is suitably adjusted.

According to one embodiment, the microcontroller can perform LF/HFcommunication and UWB communication at least partially in parallel, withthe advantage of saving time.

According to a further embodiment, it can be provided that the LFreception circuit and/or the UWB transmission and reception circuits areconfigured to assume an energy-reduced state in which they are not readyfor reception and not ready for transmission compared to their normaloperating state, and are coupled to a motion sensor in such a way thatwhen the ID transmitter is moved, the LF reception circuit and/or theUWB transmission and reception circuits are transferred into the normaloperating state.

Furthermore, it can be provided that the ID transmitter is configured inthe form of an ID transmitter that can be activated in exclusivelypassive manner, the housing of which is configured with an operatingelement that cannot be activated manually. As a result, the IDtransmitter can be used as a key fob and serves only for passivefunction release.

For key fob functionality, the ID transmitter can have a mechanicalcoupling element for coupling a key.

A second ID transmitter can be provided, which is configured in the formof a manual HF radio key in such a way that by manual actuation of abutton arranged on the second ID transmitter, an HF request signaladapted to the vehicle control unit is transmitted to request a vehiclefunction. Together with the ID transmitter, the second ID provider formsan authentication system. The two ID encoders of the authenticationsystem can be mechanically connected to each other with the mechanicalcoupling element, for example, a key ring, whereby no communicationbetween the two is permitted.

According to this idea, a key system consisting of the ID transmitterand the second ID transmitter is provided, the keys being configured forcommunication with the same vehicle but not for communication with eachother. This concept enables a physical separation between passive IDtransmitter and active ID transmitter (the second ID transmitter), whichhas the advantage that two ID transmitters working independently of eachother, depending on their equipment, are each allowed completeauthentication to the vehicle and can therefore also be used separatelyfrom each other. However, if one of them is not functional, for example,due to an empty battery, both can also serve as a backup for each other.

Another idea of the invention relates to a method. The method providesfor a vehicle authentication system to be operated in order toauthenticate a portable ID transmitter to the vehicle. Theauthentication has the purpose of releasing a vehicle function for anoperator carrying the portable ID transmitter.

The authentication system comprises the portable ID transmitter and avehicle authentication arrangement.

The authentication arrangement comprises a plurality of UWB antennas, atleast a first UWB antenna and a second UWB antenna. The first UWBantenna and the second UWB antenna are spaced apart on the vehicle. Themethod provides at least the following steps:

A) selecting a UWB antenna from the plurality of UWB antennas in theauthentication arrangement as the selected UWB antenna. The UWB antennamust be selected at least

-   -   depending on a received signal strength or multiple received        signal strengths of at least one LF signal transmitted between        the authentication arrangement and the ID transmitter, and/or    -   depending on a received signal strength or multiple received        signal strengths of at least one HF signal transmitted between        the ID transmitter and the authentication arrangement, with both        transmission directions being possible, and/or    -   depending on at least one proximity signal from one or more        proximity sensors located on the vehicle;

B) controlling the selected UWB antenna to perform UWB communicationbetween the ID transmitter and the authentication arrangement;

C) performing the UWB communication between the ID transmitter and theauthentication arrangement;

D) detecting the running time of a UWB signal of the UWB communicationbetween the ID transmitter and the selected UWB antenna;

E) checking whether the running time of the UWB signal is less than apredetermined maximum running time.

According to the invention, a selected UWB antenna is chosen from theplurality of UWB antennas before controlling a UWB antenna to performUWB communication. By choosing a selected UWB antenna, it is possibleunder favorable circumstances to obtain the information required fordistance determination by controlling only a part of the UWB antennas ofthe authentication arrangement. If this is the case, further UWBcommunication using the other existing UWB antennas of theauthentication arrangement can be relinquished. Thus, with the inventivemethod, it can be achieved that the energy required to perform UWBcommunication during an authentication process is reduced in anadvantageous manner.

Preferably, the first UWB antenna is part of a first UWB transceiver andthe second UWB antenna is part of a second UWB transceiver. This allowsfor a compact design and simple configuration.

According to the invention, it is provided that the selected UWB antennais controlled. By controlling the selected UWB antenna, it is possibleto enable UWB communication between the ID transmitter and theauthentication arrangement.

For the transmission of a UWB signal, the ID transmitter described aboveis used, which, in turn, triggers via a UWB transmission and receptioncircuit (preferably configured in the form of a UWB transceiver) thetransmission of a UWB signal, which is then detected and receives aresponse by the selected UWB antenna, whereupon the response transmittedas a UWB signal is detected and evaluated by the ID transmitter.

For example, to technically control the selected UWB antenna, it can beprovided that the authentication arrangement comprises UWB transceivers,which include a UWB antenna as a component. For example, during normaloperation, it can be provided that the first UWB transceiver is in anon-transmission and non-reception-ready state with the first UWBantenna, and, after a UWB antenna selecting has been selected, a vehiclecontrol unit controls the UWB transceiver with the selected UWB antennato put the UWB antenna into a reception-ready state. Alternatively, itcan also be provided that the vehicle control unit sets the UWB antennainto an analogous state ready for transmission and triggers thetransmission of the mentioned UWB signal via the selected UWB antenna.

By transmitting a UWB signal and responding to the UWB signal, the UWBcommunication provided for in the invention has been carried out.Subsequently, the running time of the UWB signal can recorded and theproposed test can be made of whether the running time of the UWB signalis less than a predetermined maximum running time.

If the running time of the UWB signal is less than a predeterminedmaximum running time, it can be assumed that on the vehicle no extensionof the bidirectional UWB communication has been carried out. Dependingon the safety requirements, the maximum running time can be adjusted insuch a way that, on the one hand, a sufficiently high accuracy of thedistance determination is possible. On the other hand, it can be assumedthat within the recorded maximum running time a compromise of the UWBsignal can be excluded or largely excluded.

Thus, the ID transmitter described above enables the vehicle todetermine a selected antenna from the plurality of available UWBantennas, which is then controlled to carry out UWB communication. Byselecting a UWB antenna from the available UWB antennas, the implementerof the method is provided with an opportunity for a concrete applicationto reduce the energy required for UWB communication, depending on one ormore previously recorded parameters. Depending on the practicabilityand/or security needs pursued or to be observed by the implementingdeveloper, different parameters can be used. It is advisable to use aless energy-intensive method than UWB communication for recording theseparameters or for using parameters that are already available and havealready been recorded. Based on these data, a control device, preferablya vehicle control device, can then be used to determine with which UWBantenna UWB communication is carried out and/or in which sequence thedifferent available UWB antennas are used for an UWB communication.

As indicated above, one possibility involves selecting the UWB antenna,depending on the received signal strength of an LF signal transmittedfrom the authentication arrangement to the ID transmitter. For thispurpose, the ID transmitter described at the beginning, which can bearranged for LF communications, is used. The term LF interface refers toa set of devices required for LF communication and includes at least oneLF antenna and a reception circuit coupled with the LF antenna. Such anarrangement is provided in connection with the ID transmitters mentionedabove, as well as with the inventive ID transmitters in one of itsfurther developments, as well as in many other cases. For example, an LFsignal can be transmitted from one or more LF interfaces of the vehicleauthentication arrangement to the ID transmitter, which receives it withan LF reception device and then determines the signal strength. Forexample, two LF interfaces arranged at different positions of thevehicle can each transmit a differently coded LF signal to the IDtransmitter, and the ID transmitter returns the detected signal strengthvalues, for example, in the form of RSSI values, together with therespective code of the ID transmitter, to the HF interfaces on thevehicle. Such data can then be evaluated by a vehicle control device. Asa result of the evaluation it can be determined, for example, that theUWB antenna which is closest to the LF interface with the strongest LFsignal is primarily controlled from the plurality of UWB antennas of theauthentication arrangement.

In a further development of the method, it is provided that first theabove steps B) to E) are carried out with a first selected UWB antennaand, if the running time of the UWB signal between the ID transmitterand the first selected antenna is greater than a predetermined maximumrunning time, at least steps B) to E) are carried out again. Repeatingsteps B) to E) is performed in contrast to the first performance ofsteps B) to E) with a second selected UWB antenna, with the objective ofchecking whether the running time of the UWB signal between the IDtransmitter and the second selected antenna is less than thepredetermined maximum running time.

It is therefore provided that, in addition to carrying out the inventivemethod using a first selected antenna, a second UWB antenna of theauthentication arrangement on the vehicle is selected in the event offailure to carry out a distance determination. This increases thereliability of the method. In a case in which, for example, the firstUWB antenna is shadowed—although this is unlikely—an incorrect distancedetermination result is avoided even if the ID transmitter is actuallysufficiently close to the vehicle. By repeating steps B) to E)sequentially, first with the first UWB antenna and then with the secondUWB antenna, a prioritization of the UWB antennas is performed. In manycases, this ensures that the method is already successful with the firstselected antenna. The gain in reliability is therefore not accompaniedby a disproportionately high increase in energy requirements.

Further details, characteristics, and advantages of the inventive methodand its further development are included in the following description inconnection with the drawings, in which embodiments of the invention areshown in an exemplary manner.

BRIEF DESCRIPTION OF THE DRAWINGS

It is evident that the characteristics mentioned above, as well as thosedescribed below can be used not only in the combination indicated, butalso in other combinations or individually. It is shown:

FIG. 1: shows a schematic representation of an inventive ID transmitterand an authentication system of a vehicle;

FIG. 2: shows a flow chart of an exemplary sequence of the inventivemethod.

DETAIL DESCRIPTION

FIG. 1 shows the key system 1 for an authentication system of a vehicle.The key system 1 comprises an embodiment of the inventive ID transmitter3 and a second ID transmitter 2. The ID transmitter 3 has a supplybattery 9. Also available:

-   -   a microcontroller 12,    -   UWB transmission and reception circuits 11 controlled by and        connected to the microcontroller 12 for communication with a        vehicle control unit,    -   an LF reception circuit 10 controlled by and connected with the        microcontroller 12 for receiving LF alert signals transmitted in        the LF frequency range. In addition, the ID transmitter 3 has a        housing 13, which is configured in the form of a closed housing        with no operating elements. The second ID transmitter 2 has an        HF transmission and reception interface 5, which is controlled        by a microcontroller 6 and with which a function of a vehicle is        enabled when a button is pressed on the control element 7, which        is configured in the form of a button. Only active actuation is        provided, but no passive functionality of the second ID        transmitter. A key bit 4 is provided for mechanical release of        the function. A mechanical coupling element 8 configured in the        form of a connecting ring connects the ID transmitter and the        second ID transmitter in a manner that they can be disconnected        and reconnected. Thus, the ID transmitter functions as a key        fob.

FIG. 2 involves a first possible manner of procedure of the inventivemethod using the inventive ID transmitter.

The manner of procedure shown in exemplary fashion provides that in step201 the approach of an operator to the first proximity sensor isdetected. In step 202, the proximity sensor outputs a correspondingproximity signal. By placing and coupling the first proximity sensor andthe antenna of the first vehicle UWB interface in the door handle, it isprovided that the first control means moves the first UWB antenna from anon-transmission and/or non-reception state to a transmission-readystate (step 203). With a first vehicle LF interface, an LF alert signalis transmitted (step 203) and a vehicle UWB interface is controlled bythe first control means for transferring the first vehicle UWB interfacefrom a state, which is not ready for transmission and/or reception to astate which is at least ready for reception. The ID transmitter nowtransmits a UWB signal, which receives the first vehicle UWB interface.The UWB signal transmitted responds to the UWB interface of the vehiclewith a UWB response signal (step 204). The ID transmitter receives theresponse signal and determines a running time of the UWB signal and theUWB response signal between ID transmitter and first vehicle UWBinterface. The ID transmitter transmits the running time or a parameterderived from it, preferably via UWB, to a data receiver of the vehicle(step 205). After the running time of the UWB signal between the IDtransmitter interface and the first vehicle UWB interface has beendetected, the ID transmitter checks whether the running time of the UWBsignal is less than a predetermined maximum running time. If this is thecase, the ID provider is considered to be located within the room inwhich a release is enabled (secure bubble). Furthermore, a compromise ofthe signal, for example by a relay station attack, is not considered tohave occurred. However, if it is determined in step 206 that the runningtime is greater than the predetermined maximum running time, step 208continues in the same sequence, but using the second UWB antenna.

1. A portable ID transmitter for an authentication system of a vehicle,the ID transmitter comprising, arranged in a housing: a supply battery,a micro controller, wherein the microcontroller is configured, when anLF-reception circuit has received an LF alert signal, to transmit a UWBsignal for reception by a UWB interface of the vehicle, which is coupledwith a vehicle control unit, to receive a UWB response signal, to detectthe time difference between transmitting the UWB signal and receivingthe UWB response signal, to check whether the time difference or aparameter derived from it does not exceed a predetermined maximum value,and, to transmit a radio signal to the vehicle control unit, which has arelease value, depending on the result of the test.
 2. An ID transmitteraccording to claim 1, wherein the micro controller is configured totransmit a UWB signal as a radio signal to the vehicle control unit. 3.An ID transmitter according to claim 1, wherein the micro controller isconfigured to transmit an authorization code to the radio signal.
 4. AnID transmitter according to claim 3, wherein a challenge-response listis stored on a storage medium of the ID transmitter, which storagemedium is coupled with the microcontroller, and that the microcontroller is configured to transmit by means of the radio signal aresponse value assigned to the challenge value if the UWB responsesignal comprises a challenge value.
 5. An ID transmitter according toclaim 1, wherein the ID transmitter is configured for testing a numberof LF signals for an identity identifier, detecting signal strengthvalues for the LF signals and responding to the reception of the LFsignals with an HF response signal, which comprises the identificationof the LF signal with the strongest signal strength value and/orincludes a list of identity identifiers with associated signal strengthvalues.
 6. An ID transmitter according to claim 5, wherein the UWBresponse signal is transmitted with a predetermined minimum timeinterval after the RF response signal.
 7. An ID transmitter according toclaim 1, wherein the micro controller is configured to carry out, atleast partially in parallel, an LF communication and a UWBcommunication.
 8. An ID transmitter according to claim 1, wherein the LFreception circuit and/or the UWB transmission and reception circuits areconfigured to assume an energy-reduced state in which they are not readyto receive and to transmit compared with their normal operating state,and in which they are coupled with a motion sensor in such a way thatthe LF reception circuit and/or the UWB transmission and receptioncircuits are transferred to the normal operating state when the IDtransmitter is moved.
 9. An ID transmitter according to claim 1, whereinthe ID transmitter is configured in the form of an ID transmitter thatcan be activated in an exclusively passive manner, and the housing ofwhich is configured with an operating element that cannot be activatedmanually.
 10. An ID transmitter according to claim 9, wherein the IDtransmitter has a mechanical coupling element for connecting a key. 11.A vehicle authentication system comprising the ID transmitter accordingto claim 1 and a second ID transmitter, wherein the second IDtransmitter is configured as a manual HF radio key wherein by manualactuation of a button arranged on the second ID transmitter, an HFrequest signal adapted to the vehicle control unit is transmitted torequest a vehicle function, so that the ID transmitter and the second IDtransmitter form a key system and are configured for communication withthe same vehicle, but not with one another.
 12. A method for operating avehicle authentication system for authenticating a portable IDtransmitter to the vehicle to enable vehicle functions for an operatorcarrying the portable ID transmitter, the authentication systemcomprising the portable ID transmitter and a vehicle authenticationarrangement, the authentication arrangement comprising a plurality ofUWB antennas having at least a first UWB antenna and a second UWBantenna spaced apart on the vehicle, the method comprising the followingsteps: A) selecting a UWB antenna from the plurality of UWB antennas ofthe authentication arrangement as the selected UWB antenna, wherein theUWB antenna is selected at least depending on a function of a receptionsignal strength of an LF signal transmitted between the ID transmitterand an LF interface of the authentication arrangement, and/or dependingon a function of a reception signal strength of an HF signal transmittedbetween the ID transmitter and an HF interface of the authenticationarrangement, and/or depending on a function of a proximity signal from aproximity sensor located on the vehicle; B) controlling the selected UWBantenna to perform UWB communication between the ID transmitter and theauthentication arrangement; C) performing the UWB communication betweenthe ID transmitter and the authentication arrangement; D) detecting arunning time of a UWB signal of the UWB communication between the IDtransmitter and the selected UWB antenna; E) checking whether therunning time of the UWB signal is less than a predetermined maximumrunning time.
 13. A method according to claim 12, wherein the steps B)to E) are performed with a first selected UWB antenna, and if therunning time of the UWB signal between the ID transmitter and the firstselected antenna is greater than a predetermined maximum running time,at least steps B) to E) are performed with a second selected UWB antennato check whether the running time of the UWB signal between the IDtransmitter and the second selected antenna is less than thepredetermined maximum running time representing a position of the IDtransmitter within a predetermined space surrounding the second selectedUWB antenna.